A mystery indeed! With my friend's family's holiday home in the area and his father also a surveyor, like the main man who set out on this ill fated trip, I have heard a lot about it and it appears that one of the party went mad and lost his temper.
This is a mystery without a solution and thus for the reader has a disappointing ending. However, the process of getting to the ending is generally interesting with Pearl providing a detailed description from the witnesses to the disappearance.
As a reader I would have preferred more commentary from Pearl about his thoughts about the matter rather than simply a retelling of police witness statements.
If you are keen to know a bit about Australian history, police attitudes and approaches to policing and the attitudes of 1880 Australians then it is a worthwhile read. If you are after a satisfying mystery book, then you will be disappointed.